Other wise there is no problem. The car can be driven ontill you use the heat or air conditioning.
I have looked for bubbles in the coolant when warmed up, indicating a head gasket leak.
This is a 160,000 mile "new" car with less problems that the "old" car.
No radiator leaks, hose leaks, cap holds pressure.
Antifreeze appears to boil out of reservoir but I am not certain that this is where it goes. Enough antifreeze is lost to cause the heat to stop working.